The invention relates to a wheel suspension for motor vehicles.
DE 195 33 803 discloses suspension of this type with a leaf spring arranged transversely to the vehicle. The leaf spring is mounted on the vehicle body and is articulated on the wheel carrier. Support on the vehicle body is provided by means of special elastic elements on both sides with respect to the longitudinal mid-plane of the vehicle.
The transversely arranged leaf spring has belonged to the prior art for a long time. For example, DE 61 26 40 describes a stack of springs of graded length. For a spring stack of this kind, DE 93 73 91 shows semicylindrical clamping elements arranged on both sides of the longitudinal mid-plane and oriented transversely to the longitudinal direction of the leaf spring.
DE 195 42 108 provides, for the longitudinal and transverse support of the wheel-guiding transverse leaf spring, two flexurally resistant supporting struts which are symmetrically arranged axially off-center and which are oriented at least essentially in the longitudinal direction of the vehicle and are in each case connected at one end to the transverse leaf spring in a dimensionally and angularly fixed manner by means of a clamping connection. The free ends of the supporting struts are articulated on the vehicle body via bearings containing rubber bodies and allowing a cardanic or spherical movement. The supports are intended to achieve the necessary roll-moment support in addition to the longitudinal transverse support, because the leaf spring region located between the supports is to be considered as a torsion spring acting counter to the rolling direction. Support relative to the vehicle body is obtained, here, via a level-regulating actuator arranged in the longitudinal mid-plane of the vehicle and via the bearings of the supporting struts arranged in the longitudinal direction.
The requirement demanded of a vehicle axle as regards driving stability and agility necessitates high transverse rigidity, whereas a high degree of longitudinal flexibility is necessary for good rolling comfort. Hitherto known concepts with wheel-guiding leaf springs do not satisfy this requirement. The object of the invention was to bring about the vertical and rolling suspension of a vehicle by means of a wheel-guiding leaf spring, with requirements as regards stability and comfort being taken into account at the same time.
To achieve this object, in the wheel suspension for motor vehicles with a wheel-guiding leaf spring which is arranged transversely to the vehicle, is mounted on both sides of a longitudinal mid-plane of the vehicle with respect to the motor vehicle body and is articulated on the wheel carrier (transverse leaf spring), spring arms are formed on those ends of the transverse leaf spring on which the wheel carriers are articulated, said spring arms being connected in a force-transmitting manner to the transverse leaf spring, in particular being an integral component of the transverse leaf spring. The spring arms are likewise supported relative to the motor vehicle body. Since the spring designed in this way is a universally available structural part (the spring arms can also be produced separately and then be connected positively to the transverse leaf spring), the two wheels are connected to one another directly and a function similar to that of a transverse link is achieved by means of the spring arms connected in a force-transmitting manner, in conjunction with the supports relative to the motor vehicle body. Considerably improved roll compensation is obtained by means of this combination.
The spring arms are preferably formed symmetrically with respect to the longitudinal mid-plane of the vehicle.
The spring arms point toward the longitudinal mid-plane of the vehicle and run preferably at an acute angle to the longitudinal direction of the transverse leaf spring. The spring arms and/or the end portions of the transverse leaf spring may have a curved shape. In this case, the alignments between the supports relative to the motor vehicle body and the connection point of the transverse leaf spring and spring arm are to form a triangle with an acute angle at the connection point.
It is preferred, furthermore, that the distance between the supports arranged at the end of the spring arms corresponds approximately to the distance between the supports of the transverse leaf spring.
The triangular shape formed by the support of the spring arm ends and of the transverse leaf spring on the vehicle body and by the connection at the point of articulation for the wheel carrier results directly, as an integral part of the spring, in a transverse link function by means of which longitudinal and transverse forces can be absorbed.
Different cross-sectional shapes in the longitudinal and transverse directions may be considered for the transverse leaf spring and the spring arms. By means of the different cross-sectional shapes and the local variation in the cross sections of the transverse leaf spring and of the spring arms, the individual functions of vertical suspension, roll compensation and longitudinal flexibility of the axle can be optimized separately from one another. In particular, optimization may be achieved by coordination of the radii of curvature in the vertical and/or horizontal plane and by the arrangement of the supports relative to the vehicle body. Rubber bearings relative to the vehicle body, which are arranged at the ends of the spring arms, may advantageously be used for progressive longitudinal rigidity and for damping.
In order to reduce the longitudinal rigidity of the transverse leaf spring, these may have, in particular, portions of reduced width or contractions, with the result that the longitudinal forces are absorbed to an increased extent by the spring arms.
Preferably, in the region of reduced width of the transverse leaf spring (contraction), there is arranged a web which runs perpendicularly to the surface of the transverse leaf spring and in the longitudinal direction of the latter, is oriented approximately vertically in the direction of installation and leads to increased torsional rigidity. The web itself may advantageously receive the support of the transverse leaf spring relative to the vehicle body. Roll compensation can be influenced by the design of the connection points on the vehicle body. An articulated connection allows high roll compensation; fixed clamping reduces this roll compensation.
To achieve the desired elastokinematic properties, such as, for example, roll center height, changes in toe and in camber due to compression or rolling of the vehicle and to longitudinal and lateral forces, the transverse leaf springs and the spring arms may be curved, in which case, in particular, the spring arm ends may have different radii of curvature than the transverse leaf spring. The end portions of the spring arms in the installation position may be arranged higher or lower than the transverse leaf spring. For reasons of space (for example, the height required for the transmission), in particular, the transverse leaf spring may be designed in the form of a rocker in the transverse plane of the vehicle.
The transverse leaf spring described may be produced from fiber-reinforced plastic in order to reduce the masses to be suspended, thus resulting, in particular, in a marked reduction of high-frequency vibrations. In this version, complicated rubber bearing elements for support on the vehicle body may also be dispensed with.
The transverse leaf spring according to the invention, with spring arms, may be used for the lower or the upper wheel articulation, in conjunction with a damper or with a further transverse link, but also for both wheel articulations.
Using the transverse leaf spring according to the invention, the rolling movement can be reduced to an extent such that a separate stabilizer is no longer necessary.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.